Membrane assembly driven by a biomimetic coupling reaction

One of the major goals of synthetic biology is the development of non-natural cellular systems. In this work, we describe a catalytic biomimetic coupling reaction capable of driving the de novo self-assembly of phospholipid membranes. Our system features a coppercatalyzed azide-alkyne cycloaddition that results in the formation of a triazole-containing phospholipid analogue. Concomitant assembly of membranes occurs spontaneously, not requiring preexisting membranes to house catalysts or precursors. The substitution of efficient synthetic reactions for key biochemical processes may offer a general route toward synthetic biological systems.     

A dependent theory with few indiscernibles

We give a full solution to the question of existence of indiscernibles in dependent theories by proving the following theorem: For every θ there is a dependent theory T of size θ such that for all κ and δ, κ → (δ) _T,1 iff κ → (δ) _θ ^<ω . This means that unless there are good set theoretical reasons, there are large sets with no indiscernible sequences.     

Ultrafast proton transfer of three novel quinone cyanine photoacids

Steady-state and time-resolved emission techniques were used to study the photoprotolytic properties of three recently synthesized strong quinone cyanine photoacids (QCy7 and its sulfonated derivatives). The rate coefficient of the excited-state proton transfer (ESPT), k(PT), of the three dyes is roughly 1.5 × 10(12) s(-1), a high value that is comparable to the solvation dynamics rate of large polar organic molecules in H(2)O and D(2)O. It is twice as fast as the proton transfer rate between two adjacent water molecules in liquid water. We found that, as expected, two of the sulfonated photoacids geminately recombines with the proton at an elevated rate. The accelerated geminate recombination process of the sulfonated derivatives is different from a simple diffusion process of protons. The ESPT rate coefficient of these molecules is the highest recorded thus far.     

Ultrafast excited-state intermolecular proton transfer of cyanine fluorochrome dyes

Steady-state and time-resolved emission spectroscopy techniques were employed to study the excited-state proton transfer (ESPT) to water and D(2)O from QCy7, a recently synthesized near-infrared (NIR)-emissive dye with a fluorescence band maximum at 700 nm. We found that the ESPT rate constant, k(PT), of QCy7 excited from its protonated form, ROH, is ~1.5 × 10(12) s(-1). This is the highest ever reported value in the literature thus far, and it is comparable to the reciprocal of the longest solvation dynamics time component in water, τ(S) = 0.8 ps. We found a kinetic isotope effect (KIE) on the ESPT rate of ~1.7. This value is lower than that of weaker photoacids, which usually have KIE value of ~3, but comparable to the KIE on proton diffusion in water of ~1.45, for which the average time of proton transfer between adjacent water molecules is similar to that of QCy7.     

A criterion for coarse iterability

The main result of this paper is the following theorem: Let M be a premouse with a top extender, F. Suppose that (a) M is linearly coarsely iterable via hitting F and its images, and (b) if M ^* is a linear iterate of M as in (a), then M ^* is coarsely iterable with respect to iteration trees which do not use the top extender of M ^* and its images. Then M is coarsely iterable.     

Über die directe Einführung von Hydroxylgruppen in Oxychinoline

Ohne ZusammenfassungHerrn Prof. Weidel, mit dessen Unterstützung ich vorliegende Arbeit ausgeführt habe, spreche ich an dieser Stelle meinen verbindlichsten Dank aus.     

Unraveling Π 1 1 sets, revisited

We present a method of unraveling Π ₁ ¹ sets which greatly simplifies the construction in Neeman [6]. Apart from adding elegance, this method is also useful for proofs of determinacy involving long games; see Neeman [5]. This material is based upon work supported by the National Science Foundation under Grant No. DMS-0094174.     

Theoretical evaluation of peripheral nerve stimulation during MRI with an implanted spinal fusion stimulator

This study examines the requirements for nerve excitation near a spinal fusion implant during magnetic resonance imaging. The implant is the Spinal Fusion SpF^® device manufactured by Electro Biology Inc. The electric field induced within the biological medium was calculated using a three-dimensional finite difference model (described in a separate paper by Beuchler et al. from the University of Utah). Magnetic thresholds were obtained for excitation of myelinated nerve fibers that are near the implant. Minimum (rheobase) thresholds were determined for long duration dB/dt pulses, as well as strength-duration time constants (from which thresholds at other durations could be determined) for various geometries between the implant and a myelinated nerve fiber. The lowest thresholds occur when a large (20-μm diameter) fiber is situated near the bare tip of a wire from the implant, and a long duration (2 ms) stimulus is provided for which dB/dt is constant and monophasic. Magnetic thresholds for shorter durations of dB/dt are higher in accordance with a strength-duration law. In a magnetic field having a time derivative of 10 T/s that is uniform over the torso, nerve excitation is possible under worst-case conditions only for nerve fibers that are within 0.14 mm of the bare wire tip of the implant. With 20 T/s, excitation is possible only within 1 mm of the wire tip.